C++ Program to Rotate Matrix Elements

// C++ program to rotate a matrix 
#include <iostream> 
#define R 4 
#define C 4 
using namespace std; 

// A function to rotate a matrix 
// mat[][] of size R x C. 
// Initially, m = R and n = C 
void rotatematrix(int m, int n, 
                  int mat[R][C]) 
{ 
    int row = 0, col = 0; 
    int prev, curr; 

    /* row - Starting row index 
       m - ending row index 
       col - starting column index 
       n - ending column index 
       i - iterator */
    while (row < m && col < n) 
    { 
        if (row + 1 == m || 
            col + 1 == n) 
            break; 

        // Store the first element of 
        // next row, this element will 
        // replace first element of current 
        // row 
        prev = mat[row + 1][col]; 

        /* Move elements of first row from 
           the remaining rows */
        for (int i = col; i < n; i++) 
        { 
            curr = mat[row][i]; 
            mat[row][i] = prev; 
            prev = curr; 
        } 
        row++; 

        /* Move elements of last column 
           from the remaining columns */
        for (int i = row; i < m; i++) 
        { 
            curr = mat[i][n-1]; 
            mat[i][n-1] = prev; 
            prev = curr; 
        } 
        n--; 

        /* Move elements of last row from 
           the remaining rows */
        if (row < m) 
        { 
            for (int i = n-1; i >= col; i--) 
            { 
                curr = mat[m-1][i]; 
                mat[m-1][i] = prev; 
                prev = curr; 
            } 
        } 
        m--; 

        /* Move elements of first column from 
           the remaining rows */
        if (col < n) 
        { 
            for (int i = m-1; i >= row; i--) 
            { 
                curr = mat[i][col]; 
                mat[i][col] = prev; 
                prev = curr; 
            } 
        } 
        col++; 
    } 

    // Print rotated matrix 
    for (int i=0; i<R; i++) 
    { 
        for (int j=0; j<C; j++) 
        cout << mat[i][j] << " "; 
        cout << endl; 
    } 
} 

// Driver code
int main() 
{ 
    // Test Case 1 
    int a[R][C] = {{1, 2, 3, 4}, 
                   {5, 6, 7, 8}, 
                   {9, 10, 11, 12}, 
                   {13, 14, 15, 16}}; 

    // Test Case 2 
    /* int a[R][C] = {{1, 2, 3}, 
                      {4, 5, 6}, 
                      {7, 8, 9}}; 
    */ rotatematrix(R, C, a); 
    return 0; 
}